The following has evaluated to null or missing:
==> content.summary  [in template "list_text_image.ftl" at line 87, column 94]

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Tip: It's the step after the last dot that caused this error, not those before it.
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Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
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FTL stack trace ("~" means nesting-related):
	- Failed at: ${content.summary}  [in template "list_text_image.ftl" at line 87, column 92]
	- Reached through: @article_list categoryId="${categoryI...  [in template "list_text_image.ftl" at line 67, column 18]
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